In response to the increasing capacity of flash memory, a type of storage device, and to expansion of the market for image sensors or the like designed for high-resolution cameras in mobile phones and smartphones, there arises a strong demand for high-density integration in semiconductor devices. In the manufacture of these various electronic devices, photolithographic techniques are used widely. In photolithography, efforts have been made to facilitate high-density integration by using a light source of shorter wavelength. When a KrF excimer laser or a short wavelength light source developed thereafter is used as a light source, chemically amplified resists are used in most cases and they are generally configured in the form of solutions containing a functional resin serving as a base material and a photoacid generator and further containing several types of additives. Among these components, a functional resin serving as a base material is a determinant of resist performance and it is important for such a functional resin to have a good balance of various properties including etching resistance, substrate adhesion, transparency against a light source to be used, rate of development, etc.
Functional resins for use in photoresists for KrF excimer lasers are usually polymers comprising, e.g., a vinyl compound or acrylate as a repeating unit. For example, poly(hydroxystyrene) type resins have been proposed in the case of resists for KrF excimer laser lithography (Patent Document 1), while acrylic resins whose backbone is composed of adamantyl (meth)acrylate have been proposed in the case of resists for ArF excimer laser lithography (Patent Documents 2 to 6); and hence the required backbone is now being fixed. However, polymers composed of a single type of repeating unit are not used for this purpose. This is because a single type of repeating unit cannot satisfy all of the properties including etching resistance. In actual cases, several types, i.e., two or more types of repeating units having functional groups required to improve the individual properties are used for copolymerization to give a functional resin, and the resulting functional resin is further blended with a photoacid generator and others and dissolved in a solvent for use as a photosensitive resin composition.
Recent lithographic processes have further facilitated high-density integration. ArF excimer laser lithography has continued to progress from immersion exposure to double patterning exposure, while various efforts have also been made to develop extreme ultraviolet (EUV) lithography, which receives attention as a next-generation lithographic technique, and direct writing with electron beams.
Under circumstances where developmental efforts for high-density integration have been continued, it is shown that the content of alcoholic hydroxyl groups contained in a resin composition tends to improve the sensitivity and/or resolution (see Non-patent Document 1). As an example of a resin comprising a monomer with an alcoholic hydroxyl group, a resin comprising 3,5-dihydroxy-1-adamantyl (meth)acrylate has also been proposed, by way of example (see Patent Document 7). Moreover, there is also a report showing that a chemically amplified positive resist composition which contains a resin whose repeating unit comprises a (meth)acrylic acid ester derivative having a linker introduced thereinto and an acid generator is not only good in various resist performance including resolution, but also achieves good line edge roughness (Patent Document 8).
However, to fulfill the requirement for high-density integration at 20 nm and beyond, further improvements in performance are essential, and there is a demand for further increases in the sensitivity and resolution of resists. On the other hand, when simply improving the sensitivity alone, there will arise new problems of reduced resolution and poor line edge roughness. For this reason, further studies are now conducted on resins for acid diffusion control and on combinations with various photoacid generators in an attempt to make further improvements.
Moreover, although there is knowledge of how to prepare glycerine carboxylic acid diesters (Patent Document 9), this document does not disclose a cycloaliphatic ester compound of specific structure available for use in photosensitive resin compositions and a process for preparation of this compound.